There are loads, but I've never found one that is actually good enough for decision making, as there are too many variables to take into account, which would make it far too complicated to create a thorough one. Most on the internet are very simplistic and don't actually ask the questions that need to be asked.

It's too easy to compare a profit of £50k as a sole trader against a profit of £50k as a limited company - the devil is in the detail. Eg how much of that £50k do you need to draw out of your company (different tax depending on how much is drawn compared to how much is left in). What other taxable income do you have? Do you have a spouse who could be involved in the business (sharing tax allowances etc).

Then you have a whole load of complication as regards claiming for travel costs. Different rules as to what costs are allowable for a sole trader as against a limited company. Different rules for claiming the costs of a car, whether you claim mileage or proportion of costs for business, different rules between sole trader and company as to capital allowances for car purchase, car and fuel benefits in kind for a company car regardless of mileage, etc.

Then also different rules for other expenses, such as for a mobile phone or device, for training costs, for meals/subsistence., etc.

There's a reason why there aren't any comprehensive comparison calculation websites - it's because it's impossible to make one that would be user-friendly enough yet which would include all the variables and allow for all the different rules.

I used to operate as a partnership but went Limited company a couple of years ago. For us, the tax savings have been significant. However, as pennywise says above, there are quirks or issues that you need to consider as its not exactly like for like.

In our case, we are paying less tax as there is no NI and we are only drawing salary and dividends each to the basic rate limit and leaving the rest inside the company. When partnership, we did not get that flexibility as were always higher rate taxpayers. This has allowed child benefit to be paid which was lost in the previous years. We had the earnings/spending capacity to allow flexibility.

We also had to get our mobile phones changed from personal to business. Business mobile phone contracts are not as cheap as personal. Our cars used to be dealt with on the partnership using the costs method but on the limited company they are not in the business and we use the mileage method. Pensions moved from personal contributions to employer contributions.

Accountancy costs are about 5 times more than the partnership costs as a limited company is more work.

We are better off by a long way but how much it may be for you will depend on your situation and your ability to be flexible with your income.

Everything in the above posts is true in my view, barring the extra accountancy fees which should be no more than £300 to £500 per year.

As a practising accountant, my own approach to this is to issue clients with their own personal tax calculator, based on whether they are a partnership or sole trader and the current level of profit. This factors in the extra fees and assumes 100% of profits are taken as dividends.

We then discuss what might be different in the individual case compared to the standard model. Probably the most common area of difference is the existence of a partner or adult child who could receive dividends and make the company approach more attractive.

I then guarantee the extra savings so long as the target profit is achieved and there are no legal changes. My model is fairly conservative on the likely savings so I have confidence in it, I have probably issued it to 100 or 150 people and so far no one has come back to say it did not work out for them.

You should be able to find someone local to you with a similar offering. As per the above posts and within this one, it's not just about keying the numbers in especially with the dividend tax. These days I always double check the model assumptions against my dividend tax calculator, good old Boy George made the UK tax system stupidly complex and so what used to be a simple number crunch got a whole lot harder. Glad he's gone!

Previously we used an accountant who was more book keeper than the one we use now. She couldn't do limited companies. The firm we use now does payroll and accountancy. I was including payroll in the overall costs. Plus, the 6 monthly reporting to the FCA requires a bit more work as a limited company than sole trader/partnership. So, we are using the accountant more than perhaps other businesses would.

We were paying around £270 a year as a partnership but it's over £1000 a year now including payroll. I would say we were fairly easy as things go as the information is always supplied up front. It's probably just the sheer volume of transactions over the year that is a pain with around 3-10 bank entries a day.

I'd say that £270 per year for a partnership was a very good/low price indeed. Presumably that was for a book-keeper to do it rather than a qualified accountant, which could explain why it was so cheap. But £270-£1000 isn't five times as much anyway. As Chris says, comparing like for like, i.e. using the same qualified accountant before and after the change, up to £500 more is more normal, but these days the differential is getting smaller as company accounts and now a lot simpler for small/exempt companies, so the additional cost is in dealing with set up and planning, dividends, director's payroll etc - i.e. the extra work needed.

She worked for an accountant and was qualified to a point but the accountant used to sign off on everything. In reality, he was never in the office and she ran it for years. He sold up and she set up on her own. They were a rural based firm which may explain the low cost.

Not quite! Although I was initially thinking back to the days when it was £195 (which was the figure I had in my head when I typed above). The final year was £325. The over £1000 is actually under £1000 at £996 (payroll and accounts with 6-month interim accounts to meet FCA reporting requirements). So, it's actually more like 3 times.

So, it will be a little more but that itself is not going to be a big issue unless your "earnings" are low and the margins between s/e and limited company are small. For us, the differences between the two are far far greater and more than cover the increased cost.

Thanks for these replies.
I know that there is a lot to consider, but CheapAccounting used to do one of these quick calculators, and it is no longer there. I thought another firm may do one.