Most people have correctly given their time and effort answering this, in the main this is a helpful forum and we are a community to share information, opinions and advice.
A few things you may not have considered and a reminder of others in summary.
Whichever day you complete your tax, payment is then due and as previously said you need to allow time for bank transfers to ensure HMIT receive their payment on time, if deadlines are involved. Just because it leaves you on a certain day does not ensure delivery. Banks often hold bank certain payments for security checks. In reality most arrive fine but you need to be aware of this.
You pay the tax due PLUS payment on account for the following year, the second payment 6 months later using HMIT dates
If you complete in May, the above payments immediately apply. Cashflow wise if you pay say the 25th January 2022 then there will be plenty of time for payment of any due taxes through the banking system to arrive, plus you have an increase in cashflow from May 2021 to the following January 2022. Remembering in following years you would have made two payments contribution to any future due tax.
Also remember rental is classed as a business and separate from any personal allowances.
Rent in joint names to reduce any 40% tax liability or future changes tax bands that may affect you. Hence the net profit is divided by the number of owners. If you have a lower or nil tax payer, you may wish to consider re-apportioning ownership to reduce rental taxation but remember on sale you will also have pro-rata capital allowances at the time of sale.
Expenses you can only claim those wholly for the rental property, or travel in doing so. This includes inspections. Tax allowances change each year so I’m not going into this any future.
You should also consider and plan for any future sale of your property keeping all improvement expenses separately, not repairs and renewals. I.E An improvement would be to increase the number of kitchen units, add an extension, conservatory. Add / extend anything that was not there originally. All these go towards and Capital Gains allowances. As tax laws and the percentage liability may change you must keep these separate.
You say you let out your property, some further advice, if it is your own property and not a second property (more than one), then you need to remember that if a tenant moves out and you then decide to use your own property again and move back in, you CANNOT claim for the expenses for repairs and renewals post the tenant leaving. Only expenses occurred during the tenancy may be claimed. So do any necessary whilst the tenancy is in force. Alternatively, do the necessary and let for another period of months.
If you sell your own property which was also rented, currently you need a pre let property value, sold value post letting or moving back in and use with agreed HMIT ratios for your own and let occupancy periods. The Capital Gains expenses above then kick in, legal fees, any allowances.
If you haven’t and your property is a first time let, inspect every three months, when happy twice a year then beyond will depend on any tenancy. You can claim mileage from the HMIT mileage chart. Do keep a log of all visits and why, i.e inspections, contractor visit, buying materials, inventory inspections.
Hopefully you have your answer from everyone and a bit on top to help manage your tenancy effectively.