It will shortly be time to make payment of the second HMRC payment on account for 2017/18.
There are two payments on account required for 2017/18, the tax year that ended on 5th April 2018. The first was paid by 31st January 2018, and the second is now falling due by 31st July 2018.
Payments on account for 2017/18 are initially estimated based on the 2016/17 tax return.
As the tax year ended on 5th April 2018, all the information to prepare your 2017/18 tax return should by now be available.
Should your profit have reduced in 2017/18, then submitting the tax return before the payment deadline is to be recommended – that way you can reduce the 31st July payment from an estimate to an actual amount and avoid overpaying.
Should there be a large reduction in 2017/18 income over the initial estimates, there is even the possibility of having some or all of your 31st January 2018 payment refunded.
Delaying preparing your 2018 tax return could therefore impede your cash flow should the figures have reduced.