Hi.You would need to have your accountant look at the wording of the sale agreement closely firstly to ensure that the sale proceeds cannot be seen by HMRC as future earnings subject to income tax as opposed to CGT and secondly to determine whether the consideration or sale proceeds is deemed to be ascertainable or unascertainable at the time of the sale as that will determine whether you can pay any CGT by instalments or not. If it is ascertainable then you should be able to pay the CGT by instalments. It is unascertainable then you cannot pay the tax by instalments as each instalment is normally assessed to tax in the year of receipt. The fact that you don't know exactly what the cash will be does not necessarily make it unascertainable under the relevant tax law.
If he or she hasn't already, your accountant should refer to the HMRC manual starting at CG14850 and ending at CG14980 here and compare the notes there to the sale agreement to determine whether the consideration will be deemed to be ascertainable or unascertainable at the time of the sale agreement.
You may qualify for entrepreneurs' relief which you can read about in HS275 here. If you qualified, your CGT liability would be limited to 10% of the gain as opposed to the regular 18% or 28% or a combination of the two rates. Unascertainable future consideration will not qualify for ER unless the disposal meets certain criteria outlined in CG14970 here.
It is possible to defer payment of CGT if all or part of the disposal proceeds are reinvested in new qualifying business assets which you can read about in HS290 here but not on any part of the sale proceeds which is unascertainable at the time of the sale. Again, see CG14970 here.
I hope this helps but let me know if you have any further questions.
Thank you very much Tony.This provides me with the guidance and references required.Much apprecaited.
Thanks and good luck with the business sale.