We have a business of car rentals.  We have vans which we lease out to different customers.  Some vans are booked multiple times on the same day for different periods . Is it permissible to have different hire agreements for our vans? 

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

The Answer:

It is permissible to have multiple contracts and hire agreements for a single van for different periods with different customers.
Such an agreement is binding on both parties and cannot be unilaterally revoked[1].

The Fiqh (jurisprudence of the answer):

As opposed to sales, rental agreements can be agreed to in advance for execution on a future date. The principle difference is based on the nature of the transaction; Ijarah contracts are Tamlīk of manfa’ah (usufruct), whereas, sale contracts are Tamlīk of ‘ayn (tangible asset). Imam al-Zayla’ī rahimahullah highlights the difference by stating that manfa’ah is not in existence at present, hence, the Tamlīk of it by default is suspended and forwarded until usage of an item begins[2].  

And Allah Ta’ālā Alone Knows Best
Mufti Faraz Adam,

The views and opinions expressed in this answer belong only to the author and do not in any way represent or reflect the views of any institutions to which he may be affiliated.
Arguments and ideas propounded in this answer are based on the juristic interpretations and reasoning of the author. Given that contemporary issues and interpretations of contemporary issues are subjective in nature, another Mufti may reach different conclusions to the one expressed by the author. Whilst every effort has been taken to ensure total accuracy and soundness from a Shari’ah perspective, the author is open to any correction or juristic guidance. On the event of any juristic shortcomings, the author will retract any or all of the conclusions expressed within this answer.
The Shari’ah ruling given herein is based specifically on the scenario in question.  The author bears no responsibility towards any party that acts or does not act on this answer and is exempted from any and all forms of loss or damage.  This answer may not be used as evidence in any court of law without prior written consent from the author.  Consideration is only given and is restricted to the specific links provided, the author does not endorse nor approve of any other content the website may contain.

[1]  الْإِجَارَةُ الْمُضَافَةُ صَحِيحَةٌ وَتَلْزَمُ قَبْلَ حُلُولِ وَقْتِهَا.
بِنَاءً عَلَيْهِ لَيْسَ لِأَحَدِ الْعَاقِدَيْنِ فَسْخُ الْإِجَارَةِ بِمُجَرَّدِ قَوْلِهِ: مَا آنَ وَقْتُهَا.
تَصِحُّ الْإِجَارَةُ الْمُضَافَةُ وَتَلْزَمُ قَبْلَ حُلُولِ وَقْتِهَا عَلَى قَوْلٍ؛ لِأَنَّ الْعَقْدَ قَدْ انْعَقَدَ بِحَقِّ الْمُتَعَاقِدَيْنِ وَإِنْ لَمْ يَكُنْ مُنْعَقِدًا بِحَقِّ الْحُكْمِ فَلَوْ كَانَ لِأَحَدِ الْعَاقِدَيْنِ حَقُّ الرُّجُوعِ كَانَ ذَلِكَ مُؤَدِّيًا لِإِبْطَالِ حَقِّ الطَّرَفِ الثَّانِي (الشِّبْلِيُّ) (رَاجِعْ الْمَادَّةَ 82) .
غَيْرَ أَنَّهُ لَا يَلْزَمُ قَبْلَ حُلُولِ ذَلِكَ الْوَقْتِ تَسْلِيمُ الْمَأْجُورِ لِلْمُسْتَأْجِرِ.
اخْتِلَافُ الْفُقَهَاءِ: قَدْ حَصَلَ اخْتِلَافٌ بَيْنَ الْفُقَهَاءِ فِي صِحَّةِ هَذِهِ الْإِجَارَةِ فَقَالَ بَعْضُهُمْ بِجَوَازِهَا وَقَالَ بَعْضُهُمْ بِبُطْلَانِهَا وَالْمَجَلَّةُ عَلَى قَوْلِ الْأَوَّلِ حَسَبَ قَوْلِهَا (صَحِيحَةٌ) (درر الحكام شرح مجلة الأحكام ج 1 ص 479 ط دار الجيل)

قَالَ قَاضِي خَانْ وَذَكَرَ شَمْسُ الْأَئِمَّةِ السَّرَخْسِيُّ: أَنَّ الْإِجَارَةَ الْمُضَافَةَ تَكُونُ لَازِمَةً فِي إحْدَى الرِّوَايَتَيْنِ وَهُوَ الصَّحِيحُ،(حاشية ابن عابدين ج 4 ص 401 ط سعيد(

[2]  قَالَ – رَحِمَهُ اللَّهُ – (وَتَصِحُّ الْإِجَارَةُ وَفَسْخُهَا وَالْمُزَارَعَةُ وَالْمُعَامَلَةُ وَالْمُضَارَبَةُ وَالْوَكَالَةُ وَالْكَفَالَةُ وَالْإِيصَاءُ وَالْوَصِيَّةُ وَالْقَضَاءُ وَالْإِمَارَةُ وَالطَّلَاقُ وَالْعِتْقُ وَالْوَقْفُ مُضَافًا) أَيْ مُضَافًا إلَى الزَّمَانِ الْمُسْتَقْبَلِ؛ لِأَنَّ الْإِجَارَةَ تَتَضَمَّنُ تَمْلِيكَ الْمَنَافِعِ وَالْمَنَافِعُ لَا يُتَصَوَّرُ وُجُودُهَا فِي الْحَالِ فَتَكُونُ مُضَافَةً ضَرُورَةً، وَلِهَذَا قُلْنَا تَنْعَقِدُ سَاعَةً فَسَاعَةً عَلَى حَسَبِ وُجُودِ الْمَنْفَعَةِ وَحُدُوثِهَا عَلَى مَا بَيَّنَّاهُ فِي أَوَّلِ الْكِتَابِ، وَهَذَا هُوَ مَعْنَى الْإِضَافَةِ وَفَسْخُهَا مُعْتَبَرٌ بِهَا فَتَجُوزُ إضَافَتُهُ. أَلَا تَرَى أَنَّ الْبَيْعَ لَمَّا لَمْ يَجُزْ إضَافَتُهُ لَا يَجُوزُ إضَافَةُ فَسْخِهِ أَيْضًا إلَى الزَّمَانِ وَهُوَ الْإِقَالَةُ؛ لِأَنَّهُ مُعْتَبَرٌ بِهِ  (تبيين الحقائق ج 5 ص 148 ط إمدادية)